L9911 Datasheet, PDF (1/15 Pages) STMicroelectronics – CAR ALTERNATOR MULTIFUNCTION SMART VOLTAGE REGULATOR

L9911
CAR ALTERNATOR MULTIFUNCTION SMART VOLTAGE
REGULATOR
PRELIMINARY DATA
1 Features
■ FULLY MONOLITHIC DESIGN
■ HIGH SIDE FIELD DRIVER
■ THERMAL PROTECTION
■ FIELD SHORT CIRCUIT PROTECTION
■ PROTECTED DIAGNOSTIC LAMP DRIVER
■ PROTECTED HIGH SIDE RELAY DRIVER
■ COMPLEX DIAGNOSTICS
■ LOAD RESPONSE CONTROL
■ DFM OUTPUT (FIELD MONITOR)
2 Description
The L9911 is a monolithic multifunction alternator
voltage regulator intended for use in automotive
application. It includes the control section, the field
power stage, fault diagnostic circuit which drives a
warning lamp, and the protection against short cir-
cuits.
3 Circuit Operation
The alternator's voltage regulator performs the fol-
lowing main functions:
– 1) voltage regulation
– 2) protection
– 3) control fault diagnosis
– 4) load response control
Figure 1. Package
Multiwatt8
Table 1. Order Codes
Part Number
L9911A
L9911B
Package
Multiwatt8
Multiwatt8
Features
See Table.9
See Table.9
ance so high to cause a superimposed ripple on
the alternator voltage higher than 5-6V. Conse-
quently it doesn't need, in the standard applica-
tion, any external component. Anyway an external
capacitor (2.2µF) must be inserted between A+
and ground when using the device with very long
cables.
3.2 PROTECTION
It is present a protection against short circuits of
the lamp and the relay power drivers (L) and of the
field power driver (F+), a thermal drivers shutdown
protection and an overvoltage protection of L pow-
er drivers.
3.1 VOLTAGE REGULATION
The alternator voltage is compared with a refer-
ence voltage in an amplifier, whose output deter-
mines the switching frequency of output power
MOS whose current excites the coil of the alterna-
tor; as the regulator is in fixed-frequency topology,
the field switching frequency does not depend on
the alternator characteristics. The regulators have
an integrated filter in the voltage sensing path
guaranteeing the correct behaviour of the devices
also when the rectifier diodes feature very high
switching spikes. The internal filtering allows the
usage of the device also with very long cables con-
necting the alternator to the battery with an imped-
3.3 DIAGNOSIS
The circuit detects fault conditions related to the
phase and F+ status and receives informations
from one of the three alternator phases. In order to
prevent spurious indications, fault warnings are
not displayed immediately but are dalayed by a
fixed time.
3.4 LOAD RESPONSE CONTROL
The internal circuit regulates the soft start charac-
teristics (activated always at engine start) and the
soft attack characteristics.
November 2005
Rev. 3
1/15
This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice.